The present invention relates generally to an information/data recording disk apparatus such as a magnetic disk apparatus, CD-R (compact disk recordable), DVD (digital versatile disk) and the like disk apparatus. More specifically, the invention is concerned with an apparatus for detecting shocks, vibrations and the like applied to the disk apparatus to thereby prevent erroneous operations thereof which may be brought about by such unwanted phenomena.
In recent years, the disk apparatus such as magnetic disk apparatus is increasingly employed in various machines, apparatuses and/or equipment such as, for example, portable-type computer and others, being accompanied with a trend of the magnetic disk apparatus being implemented in a thin and small-sized structure. In the portable-type apparatuses such as those mentioned above, the magnetic disk apparatus mounted therein is likely to be subjected to shocks and vibrations applied externally. When rotational vibration or rotational shock around an axis perpendicular to a disk surface or plane of a magnetic disk is externally applied to the disk apparatus, then the magnetic head positioning control system of the magnetic disk apparatus will undergo the influence of the angular acceleration brought about by the rotational vibration or rotational shock, which may result in that the position of the magnetic head (or write/read head) is caused to displace or deviate from the center of the track to which the head is positioned by the head positioning control system. This event will hereinafter be referred to as the off-track event or simply as the off-track. Further, when translational vibration or translational shock is externally applied to the magnetic disk apparatus, the translational acceleration is translated into angular acceleration due to mass unbalance of the head supporting arm assembly, as a result of which the off-track event of the magnetic head is brought about. As can readily be understood, such off-track event may involve destruction of data recorded on the disk, degradation of the performance of the magnetic disk apparatus, etc. In this conjunction, a great difficulty will be encountered in controlling the magnetic head such that it can follow the target track perfectly notwithstanding of the disturbance of angular acceleration applied externally due to irregular shocks, vibrations and/or the like.
Under the circumstances, an attempt of coping with the above-mentioned problem has been developed and disclosed in Japanese Unexamined Patent Application Publication No. 45024/1997 (JP-A-9-45024). More specifically, disclosed in this publication is a method of detecting shocks and vibrations in a plane parallel to that of the magnetic disk with the aid of three acceleration detecting sensors, i.e., two acceleration sensors dedicated for detection of the acceleration in two directions extending discretely in parallel to each other in a plane substantially parallel to that of the magnetic disk and the sensor for detecting acceleration in one direction which is not in parallel with the two directions mentioned just above, wherein the three acceleration sensors are mounted on a box-like housing or casing of the magnetic disk apparatus or a circuit board such as a printed circuit board which is mounted internally of the box-like casing. Incidentally, in the magnetic disk apparatus disclosed in the above-mentioned publication, the acceleration sensors are disposed along side walls, respectively, of the box-like casing or the circuit board.
With a scheme for detecting the acceleration by using a single sensor, only the translational acceleration can be detected by that sensor. More specifically, as to the angular acceleration, the sensor detects the translational acceleration which is brought about by the angular acceleration in the vicinity of the sensor. Accordingly, in the case where the center of rotation for the angular acceleration exists in the vicinity of a straight line representing the sensing direction of the sensor, the acceleration is too low for the sensor to detect it. In other words, the angular acceleration for which the center of rotation lies close to the sensor can not be detected by that sensor. On the contrary, in the case of the angular acceleration for which the center of rotation exists at a position distanced sufficiently from the straight line representing the sensing direction of the sensor, the translational acceleration can be detected by the sensor with sufficiently high sensitivity. In this conjunction, it is noted that the angular accelerations acting on the magnetic disk apparatus in the state mounted, for example, in a portable computer may have a variety of positions in respect to the center of rotations thereof, as a result of which the acceleration detection output of the sensor may vary remarkably for a same angular acceleration. Such being the circumstances, great difficulty is encountered in actual applications in setting a threshold value or level for allowing a write operation disabling or inhibiting signal to be generated upon occurrence of the off-track event in response to the output of the single acceleration sensor.
In this conjunction, it is disclosed in JP-A-9-45024 mentioned above that difference between the outputs of two sensors which are so disposed as to detect the acceleration in the directions extending discretely in parallel to each other is used for detecting the angular acceleration. Theoretically, the angular acceleration must be detected with such arrangement. However, the sensors employed for detecting the accelerations in practical applications suffer remarkable dispersion or deviation in respect to the detection sensitivity due to intrinsic differences inherent to the individual sensors, environmental conditions and the secular change. By way of example, it is known that the acceleration detecting sensors known heretofore have dispersion of about 20%. Consequently, even if the acceleration detecting sensors are so disposed as to detect the acceleration in the two directions extending discretely in parallel to each other, it is difficult to detect only the angular acceleration due to the dispersions of the detection sensitivity between the sensors, incurring the problem that the translational acceleration may erroneously be detected as the angular acceleration.
Furthermore, the sensor output is easily susceptible to the influences of noises such as power source noise and the like. Accordingly, disposition of the two acceleration sensors on the side walls, respectively, of a circuit board which extend in parallel with each other, as disclosed in JP-A-9-45024, will be accompanied with such a problem that the sensor output contains lots of noise because of a large distance intervening between the sensors and the circuit for processing the sensor outputs, making it difficult to detect the angular acceleration with high sensitivity and reliability.
In practical applications, it has been found that the translational acceleration in the direction perpendicular to the plane of the disk brings about lesser off-track displacement of the read/write head when compared with that bought about by the translational acceleration in a plane parallel to that of the disk. Accordingly, in case the threshold value for allowing the write operation disabling signal to be generated through comparison is set for the translational acceleration of the perpendicular direction, the detection sensitivity will become lowered in the direction parallel to the disk plane, which may lead to occurrence of the off-track event and hence to the data destruction, giving rise to a serious problem. On the contrary, when the threshold level mentioned above is set in consideration of the translational acceleration in the plane parallel to the disk plane, such translational acceleration of perpendicular direction which can inherently irrelevant to the data destruction will be detected as well, as a result of which the write operation inhibit signal is unnecessarily produced, involving degradation of the operation performance of the magnetic disk apparatus. In brief, compatibility between security of the operation performance and protection of the data is difficult to realize.
It should additionally be mentioned that in the small type magnetic disk apparatus for the portable equipment in the current state of the art, difficulty will also be encountered in disposing the sensor in a region extending from a pivot shaft to a voice coil motor from the standpoint of implementation of the thin and small-sized magnetic disk apparatus.
In the light of the state of the art described above, it is an object of the present invention to provide an information recording disk apparatus destined to be mounted in a portable equipment, which apparatus is equipped with facilities for preventing occurrence of the off-track event due to disturbance to thereby protect positively data from destruction and assure read/write operations with high accuracy and reliability.
Another object of the present invention is to provide a magnetic disk apparatus destined to be mounted in a portable equipment such as a small-size computer, which apparatus is capable of preventing occurrence of the off-track event due to disturbance, protecting positively data from destruction and assuring read/write operations with high accuracy and reliability.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to an aspect of the present invention a magnetic disk apparatus which includes at least a magnetic disk for recording information, at least a magnetic head for writing/reading the information on/from the magnetic disk, a head supporting arm assembly for supporting the magnetic head, a pivot shaft for supporting pivotally the head supporting arm assembly, an actuator for driving the head supporting arm assembly, and at least a pair of acceleration detectors for detecting acceleration in two directions extending discretely in parallel to each other, wherein the pair of acceleration detectors are disposed on the box-like casing or alternatively a circuit board mounted internally of the box-like casing of the magnetic disk apparatus at positions closer to the magnetic disk relative to the pivot shaft as viewed in a longitudinal direction of a box-like casing of the magnetic disk.
In a preferred mode for carrying out the present invention, the magnetic disk apparatus may be so arranged that the distance between straight lines indicating direction of the acceleration detected by the two acceleration detectors, respectively, is not less than 10% and not more than 80% of a longitudinal length of a box-like casing of the magnetic disk apparatus.
In another preferred mode for carrying out the present invention, the acceleration detector for detecting acceleration in a plane which forms an angle of not greater than 10 degrees relative to a plane extending in parallel to the plane of the magnetic disk may be mounted on a box-like casing or a circuit board which is mounted internally of the box-like casing of the magnetic disk apparatus.
In yet another preferred mode for carrying out the present invention, the magnetic disk apparatus may be so arranged that a sensor or detector for detecting an angular velocity around an axis perpendicular to a plane of the disk and an acceleration detector for detecting acceleration in a plane direction which forms an angle of not greater than 10 degrees relative to the plane of the magnetic disk are mounted on the box-like casing of the magnetic disk apparatus or alternatively on the circuit board which is mounted internally of the box-like casing of the magnetic disk apparatus.
In still another preferred mode for carrying out the present invention, the magnetic disk apparatus may be so arranged that an acceleration detector for detecting an angular velocity around an axis perpendicular to a plane of the magnetic disk and acceleration detectors for detecting accelerations, respectively, in the two directions which are parallel and do not coincide with each other in a plane which forms an angle of not greater than 10 degrees relative to the plane of the magnetic disk or alternatively one IC chip incorporating the two acceleration detectors mentioned just above are mounted on the box-like casing of the magnetic disk apparatus or the circuit board mounted internally of the box-like casing thereof.
By virtue of the arrangements described above, the angular acceleration applied to the box-like casing can positively be detected with at least two acceleration detectors disposed in parallel to each other. Besides, the magnetic disk apparatus can be realized in a small-sized structure.
Further, even when dispersion is found between the two acceleration detectors at the least which are disposed in parallel with each other, the angular acceleration applied to the box-like casing of the magnetic disk apparatus can be detected with an enhanced sensitivity.
Furthermore, the acceleration on the order of 10G applied to the box-like casing in the direction perpendicular to the plane of the disk as well as the acceleration and the angular acceleration appearing in a plane parallel to the disk plane under the influence of deformation of the circuit board on which the acceleration detectors are mounted can be detected with an improved sensitivity.
Besides, the rotational shock/vibration of very small magnitude applied to the box-like casing which could not be detected heretofore with two acceleration detectors having different sensitivities and disposed in parallel to each other can be detected with high sensitivity with the acceleration detecting arrangement incorporated in the magnetic disk apparatus according to the present invention.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.